As electronic devices have been reduced in size and increasingly highly integrated in recent years, radiated electromagnetic noises tend to be generated in a printed board used in the electronic devices and a flexible printed wiring board which connects the printed boards, and these boards are easily affected by external noises.
An example of a measure for reducing the generation and influence of the electromagnetic noises is a twisted pair structure wherein a differential wiring is used. In the Patent Document 1, for example, a structure illustrated in FIG. 6 (hereinafter, referred to as a first conventional example) was proposed as a structure of the flexible printed wiring board in which the electromagnetic noises are reduced. According to the first conventional example, a wiring pattern layer provided on a surface side of a flexible printed wiring board having a bilayer structure is patterned so that a plurality of surface wirings 528 in parallel with one another and tilted downward from left to right are obtained, a wiring pattern layer provided on a rear-surface side thereof is patterned so that a plurality of rear-surface wirings 529 intersecting with the surface wirings 528, in parallel with one another, and tilted upward from left to right (viewed from the surface side) are obtained, and end portions of the surface wirings 528 and the rear-surface wirings 529 are connected through inter-layer connection vias 530. As a result, the twisted pair structure is formed as a whole.
The Patent Document 2 proposed a structure illustrated in FIGS. 7A and 7B (hereinafter, referred to as a second conventional example) as a structure of a flexible printed wiring board in which the electromagnetic noises are reduced. According to the second conventional example, a first wiring pattern 602 and a second wiring pattern 603, for which a signal having a phase electrically different to that of the first wiring pattern 603 through 180 degrees is driven, are formed in a wave shape on a wiring pattern layer provided on a surface side of a flexible printed wiring board having a monolayer structure, and the twisted pair structure is formed so that the phase difference between the first wiring pattern 602 and the second wiring pattern 603 is 180 degrees when the wiring board is bent along a bending line 618.    Patent Document 1: 2001-60746 of the Japanese Patent Applications laid-Open    Patent Document 2: 2002-204042 of the Japanese Patent Applications laid-Open